This invention relates to the method and apparatus for determining the size and mass distribution of a randomly sized sample of particles. More specifically, our invention uses a series of liquid-cyclones and a radiation attenuation detector to arrive at the discrete fractions of particle mass and size separated.
In the mining and metallurgy field, rapid determination of the size and mass distribution of a random size sample of particles is important for several reasons. For many processes, knowledge of the size and mass of particles is a critical factor in monitoring, controlling, and optimizing the performance. For example, in the mineral beneficiation industry where comminution, the reduction of particle size, accounts for a major source of the processing costs, overgrinding can significantly increase the plant production costs; while undergrinding would not liberate the minerals and would result in lower recoveries. Since, the amount of grinding required is directly related to the size of particles involved, knowledge of this area is all important.
Our invention attempts to optimize to the smallest value the amount of comminution required by rapidly analyzing a sample of random sized particles in an on-stream control application. In the prior art, samples have been analyzed by the use of a variety of methods. Many of these methods are limited in their application because of the need for a highly dispersed and diluted feed sample, nonopacity of the fluid medium, the use of a very small sample weight which can result in processing a nonrepresentative sample, the extrapolation of size distribution from very limited data, and the use of a difficult and lengthy standardization procedure. Of the known prior art, U.S. Pat. No. 3,505,519 to M. G. Fleming et al comes the closest in its operation to our invention. However, it differs in several important features from what we will describe. The biggest differences are that we separate the randomly sized particles into discrete fractions and the method by which this is accomplished. The separation method we employ insures discretely sized fractions that are better suited for the detection step which follows.